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Factors that power up building-integrated photovoltaics

Professor Taehoon Hong, the head of research group (left) & Mr. Choongwan Koo, the lead authorDepartment of Architecture & Architectural Engineering, Yonsei University

■ Engineering & Technology /

Factors that power up building-integrated photovoltaics

New research suggests variables end-users should consider before installing photovoltaic blinds.

Solar photovoltaic (PV) energy is a sustainable and clean energy source that permits distributed generation and provides more innovative electrical infrastructure. Building-integrated PV (BIPV) systems appeal to end-users in highly populated urban areas who want to achieve zero-energy buildings; however, their technical and economic performance depends on variables such as equipment design and client goals.

Professor Taehoon Hong of Yonsei University led the research, collaborating with Choongwan Koo, Jeongyoon Oh, and Kwangbok Jeong to improve the understanding of the nonlinearity of the shading effect on the technical-economic performance of a building-integrated photovoltaic blind (BIPB).

Previous studies have considered the shading effect of the BIPB applied to a building façade. But, according to Professor Hong, “it is not enough to conduct the nonlinearity analysis of the shading effect due to the complex relationship among the design variables of the BIPB.” The design variables considered, in this case, are the orientation and slope of the blind, the width of the PV panel, and the season.

Building-integrated photovoltaic blinds are an option in the pursuit of zero-energy structures.

The research also sheds light on the economic performance of the BIPB and evaluates the feasibility of the BIPB before its installation. Professor Hong adds that the study suggests variables to consider so that “the BIPB will meet the client expectations on various project objectives;” specifically, the amount of electricity generation per unit area from the BIPB, the net present value (NPV), and the saving-to-investment ratio (SIR) from a life cycle perspective are considered.

The researchers conducted building energy simulation to estimate the amount of energy generated from the BIPB considering the shading effect. The simulations were based on an elementary school in Pusan, in South Korea, with the following characteristics: 62.3% visible transmittance, 415.8 m2 of the exterior window area, and 11.7% panel efficiency.

For the economic performance analysis, the study used the present worth method and considered the discount rate and costs of ownership.

In terms of technical performance, the study found that the blind’s slats can have a nonlinear effect on the amount of energy generated, and more energy is produced in summer than in winter. However, the amount of energy generated also depends on the blind’s orientation and slope, the width of the PV panel, and the season. For example, as the width of the PV panel increases, the energy generated per unit decreases due to the shading effect.

The economic performance can change depending on the type of investment values, absolute investment or relative investment. From a life cycle investment perspective, as the width of the PV panel increases, the NPV increases, but the SIR decreases.

In sum, clients who intend to install BIPBs should consider design and economic variables before installation to ensure that their expectations are met. Design variables include the orientation and slope of the blind, the width of the PV panel, and the season. Economic variables include the absolute investment value and the relative investment value.